Triketones have been used for many years as herbicides for the control of undesired vegetation. Herbicidal triketones have been described, for example, in EP-A-338992, EP-A-336898, U.S. Pat. No. 4,869,748, EP-A-186118, EP-A-186119, EP-A-186120, U.S. Pat. No. 4,202,840, U.S. Pat. No. 4,695,673, U.S. Pat. No. 4,780,127, U.S. Pat. No. 4,921,526, U.S. Pat. No. 5,006,150, U.S. Pat. No. 5,545,607, U.S. Pat. No. 5,925,795, U.S. Pat. No. 5,990,046, U.S. Pat. No. 6,218,579, EP-A-249150, EP-A-137963, EP-A-394889, EP-A-506907 or EP-B-135191. Examples of herbicidal triketones are inter alia Sulcotrione (MIKADO®) whose chemical designation is 2-(2-chloro-4-methanesulfonylbenzoyl)-1,3-cyclohexandione, 2-(4-methylsulfonyloxy-2-nitrobenzoyl)-4,4,6,6-tetramethyl-1,3-cyclohexane dione; 3-(4-methylsulfonyloxy-2-nitrobenzoyl)-bicyclo-[3,2,1]octane-2,4-dione; 3-(4-methylsulfonyl-2-nitrobenzoyl)-bicyclo-[3,2,1]octane-2,4-dione; 4-(4-chloro-2-nitrobenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H, 6H)-dione; 3-(4-methylthio-2-nitrobenzoyl)-bicyclo[3,2,1]octane-2,4-dione; 4-(2-nitro-4-trifluoromethoxybenzoyl)-2,6,6-trimethyl-2H-1,2-oxazine-3,5(4H, 6H)-dione.